Abstract: The continuous improvement of people’s living standards and quality puts higher and higher demands on polymer materials, and damping materials such as polyurethane elastomer used for vibration and noise reduction have also received increasing attention. However, the application of polyurethanes is limited to some extent owing to the narrow effective damping temperature range of polyurethane. Therefore, polyurethane containing a branched chain has been prepared from the perspective of its structural designability, in which the prepolymer synthesized by the reaction of polyethylene glycol monomethyl ether (MPEG) with toluene 2,4-diisocyanate (TDI) is performed as a branched chain. Herein, the long branched chain with one end fixed at the end gives its unique movement and relaxation, contributing to the superior damping performance of polyurethane to some extent, and the presence of TDI not only prolongs the length of the branch and increases the entanglement degree between the branches and the molecules but also makes the branches contain a strong polar electron-withdrawing isocyanate group and a urethane group, impacting the branch and the main chain with strong hydrogen bonding effect. Herein, the influencing factors of polyurethane on damping property are explored separately from the perspective of hydrogen bonding and microphase separation. By means of Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), atomic force microscopy (AFM), and broadband dielectric relaxation spectroscopy, the results show that E'_{30 °C}/E'_{70 °C} is able to reach 268.28 with the increased proportion of branches, indicating the dropped degree of microphase separation of polyurethanes. Furthermore, the hydrogen bonding effect is enhanced by characterization with FTIR. The two aforementioned effects make the damping properties of polyurethanes more excellent; the effective damping (tan δ ≥ 0.3) can even exceed 150 °C (−50−100 °C). Simultaneously, the polyurethane has a certain self-healing property after the introduction of branches, which is of great significance to extend the service life of polyurethanes